The present invention is situated in the field of materials handling technology and relates to a device for conveying individually held flat articles in a dense conveying stream wherein the articles are conveyed one after the other with distances between one another (measured in the conveying direction), which usually are smaller than the dimensions of the articles parallel to their flat extent.
Conveying streams of the type mentioned above are customary in the further processing of printed products, such as in the field of dispatch room technology. In such technologies the printed products delivered from a printing machine at different time periods are processed, for example, by being combined in groups, re-arranged and/or packaged, in a manner to be able to be readied for dispatch at an outlet station.
In dispatch room technology, the printed products are conveyed in imbricated streams, in which the products lie loose on a conveying surface partially overlapping one another or are pressed onto such a surface with suitable means. In such an imbricated stream the spacing between the products corresponds to the distance between the leading edges of each two successive products. Depending on the orientation of the products in the imbricated stream, the leading edges are oriented downwards or upwards and in the case of folded products the folded edge or the edge opposite the folded edge is the leading edge.
The orientation of the printed products in an imbricated stream can be changed, for example, by twisting or deflecting the imbricated stream such that, from a stream with leading edges lying on top, a stream with leading edges lying underneath can be formed. In doing so, the printed products are inverted (the top side is turned downwards). By reversing the conveying direction of an imbricated stream (winding up and unwinding again), the leading edges become the trailing edges, wherein the products maintain their position (the top side remains on top). However, the product sequence is inverted. For other re-arrangements, in most instances every product of an imbricated stream is individually gripped, is re-oriented and is then deposited in the stream once again. This, however, is a very elaborate operation in particular in respect to the equipment required.
Frequently used in dispatch room technology are also dense conveying streams of individually held printed products, i.e. conveying streams in which the printed products are conveyed one after the other, each one held by a gripper. The grippers are arranged one behind the other on transport elements movable along a conveying track, for example, arranged on the links of a conveyor chain, and each gripper grips and holds a flat article in an edge region, such as in the middle region of one edge. Usually, the grippers are arranged symmetrically with respect to the conveying track of the transport elements, i.e., there is a plane, in which the conveying track is situated and which cuts the grippers conveyed one behind the other into two functionally equivalent parts. In many instances, the grippers are swivelling parallel to the direction of conveyance either freely or in a controlled manner. The transport elements are usually moved in guide channels, which may have a curved course and if so required may be twisted.
Printed products being conveyed in a held manner can be arranged perpendicular to the conveying track (e.g., for horizontal conveyance, they are suspended vertically downwards from the grippers), so that, even if the distances between the products are smaller than the flat extent of the products, there is no overlapping and there are no leading and trailing edges. However, as soon as the products in the conveying stream are not arranged precisely perpendicular to the conveying direction, they overlap one another in a similar manner as in an imbricated stream and there are leading and trailing edges.
In a conveying stream, in which products are conveyed individually held by grippers, the products can be re-orientated in more ways and in a simpler manner than is the case in an imbricated stream. In particular, it is possible by simply displacing the edges opposite the held edges from a leading to a trailing position, to reverse the products (the leading edge becomes the trailing edge, the product top side becomes the bottom side).
It is an object of the invention to create a device for held conveyance of flat articles in a dense conveying stream, with which device even more re-orientations of the flat articles shall be possible during conveyance and in a more simplified manner than is possible with known devices serving the same purpose. Therefore, the device can be used universally in the most diverse applications. Nonetheless, the device will not be significantly more complicated and elaborate than known devices for held conveyance of flat articles.
In accordance with the present invention, the device includes a plurality of grippers for gripping and holding the flat articles in an edge region. The grippers are designed to be opened and closed in a controlled manner. Each gripper is arranged on a gripper arm, the gripper arm being arranged on a transport element from which it projects to one side. The transport elements are movable along a conveying track and they are connected together in a chain or they are independent of one another and they move along the conveying track driven by a suitable drive, for example, guided in a suitable guide channel. The grippers are designed to rotate without limitation around the gripper arm, i.e., in essence by 360xc2x0.
By rotating the grippers around the gripper arms during conveyance, flat articles held gripped by the grippers can be brought into the most diverse spatial positions relative to the conveying track of the transport elements. For changing their orientations, the flat articles can also be moved through between adjacent grippers. As shown further on, the articles can be brought into all possible orientations in the stream if, in addition to the unlimited gripper rotation, it is possible to arrange the conveying track to be deflected and/or twisted. Depending on the application, the rotational position of the grippers in one area can also be changed over time. Therewith it is easily possible to change the device according to the invention for receiving articles supplied with-various orientations and delivering them in always the same orientation.
For a re-orientation that necessitates a movement of the flat articles between adjacent grippers, the spacing between the grippers may need adjustment to the format and to the flexibility of the flat articles. If the grippers are arranged on individual transport elements being movable along the conveying track in a substantially independent manner, local enlargement of the spacings between the grippers is no problem at all.